Liquid wastes are produced by most human activities including domestic sewage, agricultural processes and industrial operations. For example, according to the U.S. Department of Commerce, industrial water users discharge approximately 285 billion gallons of wastewater daily.
Some types of conventional wastewater treatment processes are microbiologically mediated. Municipal, agricultural and industrial wastewater is often treated aerobically, thereby converting pollutants into environmentally acceptable analogues. The addition of micro-bubbles of oxygen has been demonstrated to be an effective enhancement of the aerobic treatment of wastewater to lower biological oxygen demand (BOD), total dissolved solids (TDS) and total organic carbon (TOC).
Anaerobic wastewater treatment methods have also been used. For example, the addition of hydrogen has been found to enhance anaerobic processes, and to reduce unsaturated organic liquids and sludges. Anaerobic digestion is one of the oldest processes used for the stabilization of sludges. It involves the decomposition of organic matter and inorganic matter in the absence of molecular oxygen. During conventional anaerobic digestion, the organic matter in mixtures of primary settled and biological sludges is converted biologically, under anaerobic conditions, to produce methane (CH4) and carbon dioxide (CO2). During conventional anaerobic digestion, a consortium of organisms converts organic sludges and wastes. One group hydrolyzes organic polymers and lipids. A second group of anaerobic bacteria ferments the breakdown products to simple organic acids. A third group of microorganisms converts the hydrogen and acetic acid to methane gas and carbon dioxide.
Gas-liquid mixing systems are used in various processes and methods employed in the wastewater industries. Many types of mechanical devices and mixers have been developed to improve wastewater treatment by enhancing gas-liquid mixing. By enhancing gas-liquid mixing, wastewater aerobic treatment processes are improved through increased oxygen (aerobic) and hydrogen (anaerobic) dissolution and residence time.
U.S. Pat. Nos. 5,916,491 and 5,925,290, which are incorporated herein by reference, disclose apparatus and methods for mixing gas and liquid through vortex or venturi devices. The mixers are particularly suited for mixing oxygen-containing gases into industrial and municipal wastewater. Other types of gas-liquid mixers are also disclosed in U.S. Pat. Nos. 3,969,446, 4,328,175, 4,454,077, Re. 32,562, 4,645,603, 4,695,378, 4,956,080, 5,061,406, 5,073,309, 5,085,809, 5,314,076 and 5,494,576, which are incorporated herein by reference.
The bioremediation of various pollutants such as chlorinated solvents and other types of pollutants using butane-utilizing bacteria is disclosed in U.S. Pat. Nos. 5,888,396, 6,051,130, 6,110,372, 6,156,203, 6,210,579 and 6,245,235 which are incorporated herein by reference.